ON MODELING PROTON AFFINITY AT THE OXIDE WATER INTERFACE

The electrostatic model predicts the point of zero net proton change of oxide/water interfaces from independent variables having the form: s/R (s is the bond valence, cation valence divided by coordination number, and R is the distance separating two ions). The electrostatic model uses bond valence s to represent the effective charge at a surface site. For each of the various electrostatic models, there is an analogous crystallochemical model that is identical in every way except that it lacks R-1 dependence. A statistical comparison of the electrostatic and crystallochemical models demonstrates that the R-1 -dependence in the electrostatic model makes no significant contribution to the correlation coefficient. The crystallochemical model, besides being a predictor of proton affinity, has close connections with the bond-valence model of hydrogen-bond structure and function. From this connection, the crystallochemical model makes qualitative predictions regarding the effect of hydrogen bonding on: (a) proton affinity; (b) the physisorption of water; and (c) surface structure. © 1993 Academic Press, Inc.